Redundant data weighting is one of the significant steps in reconstructing images from helical cone beam data in computer tomography (CT). It affects various aspects including reconstruction accuracy, susceptibility to motion artifacts and noise. In prior art, cone beam weighting (CBW) is used in helical CT with a wide cone angle to reduce cone beam artifacts, to improve detector utilization and to reduce image noise. Prior art approaches usually consider a case of 1-PI reconstruction in which a view range is less than one rotation. However, the most practical helical CT in clinical settings uses the reconstruction view range between one and two rotations for each slice.
The CBW weight function such as uCBW can be implemented in several ways. In general, regardless of implementations, streak artifacts are caused by singularity of the CBW function at Z-positions near the image plane when the rotation is equal to or more than two. In particular, when an image plane projects to a small fraction of the detector row, and the non-linear form of uCBW cannot be accurately determined for all image pixels. In other words, a weight function generally becomes narrower than the detector size. Consequently, the inaccuracies in CBW weighting manifest themselves as streak artifacts.
In view of the above and other prior art problems, a desired streak artifact reduction technique is still desired to improve the image quality for helical cone beam CT.